October 15, 2021
By Steve Douglas, Senior Technical Codes Specialist, QPS
This is the fourth in the series of articles detailing significant changes for the 2021 Canadian Electrical Code Part I (CE Code) that may impact electrical equipment manufacturers.
Through my knowledge and experience, it has been common practice for many years to install a Class 2 transformer with 15 A overcurrent protection in the primary circuit. However, the wording in the 2018 CE Code does not allow this practice.
Allowing this would mean that the primary overcurrent protection for a Class 2 transformer would be required to follow CE Code Rule 26-254 limiting the size of this overcurrent protection to 125% of the primary current. Prior to the rewrite of Section 16 in the 1978 CE Code, the 1975 edition of the CE Code allowed a 15 A overcurrent device in the primary circuit of a Class 2 transformer. This rule from the 1975 edition of the CE Code was deleted as part of a rewrite of Section 16 in the 1978 edition.
Image courtesy of QPS, depicts a Class 2 transformer connected to a 15 A branch circuit breaker.
A previous IAEI NEWS (International Association of Electrical Inspectors) article on transformer overcurrent protection raised a question by an IAEI NEWS reader regarding the maximum overcurrent protection allowed for a Class 2 transformer. As a result of the inquiry a proposal was submitted to add new Subrule 2) to Rule 16-202 Methods of installation on the supply side of overcurrent protection, transformers, or devices having Class 2 outputs. The new subrule allows a 20 A-rated overcurrent device to protect the supply side of transformers or other devices having Class 2 outputs. The rating of 20 A aligns with the product standards for transformers or other devices having Class 2 outputs.
For more information or clarification on this topic, please contact Steve Douglas at SDouglas@qps.ca
Steve Douglas is the Senior Technical Codes Specialist for QPS Evaluation Services and is an IAEI International Past President. In addition, Steve is the Immediate Past Vice Chair of the CE Code Part I, Chair of CE Code Part I Subcommittees for Section 2, 12, and 84, and a member on Sections 8, 40, 64, 68, 76, 78 and Appendix A. In addition, Steve is the Chair of the CSA Subcommittees for Standards C22.2 No. 273 Cablebus, C22.2 No. 327 HDPE Conduit, C22.6 No. 1, Electrical Inspection Code for Existing Residential Occupancies committee, SPE-1000 Working Group the Past Chair of the Technical Committee on Wind Turbines, and a member on committees for the Objective Based Industrial Electrical Code, Safety Management Systems, Energy Storage Systems, Solar Photovoltaic Modules, Industrial control panels and assemblies, Industrial Machinery, Photovoltaic Cable, Fuel Cells, Wind Turbines, Distribution transformers, Outlet Boxes, and Wiring Fittings Hardware and Positioning Devices.